The invention relates to Voice over Internet Protocol (VoIP), and more specifically, to VoIP services in personal communication networks.
Internet Voice, also known as VoIP, is a technology that allows users to make telephone calls using a broadband Internet connection instead of an analog phone line. VoIP defines a way to carry voice calls over an IP network including performing digitization and packetization of the voice streams. IP Telephony utilizes the VoIP standards to create a telephony system where higher level features, such as advanced call routing, voice mail, contact centers, etc., can be utilized.
Currently, there are some popular VoIP networks, including H.323, developed by the International Telecommunication Union (ITU), and Session Initiation Protocol (SIP), developed by the Internet Engineering Task Force (IETF). These VoIP networks provide peer-to-peer, multimedia signaling protocol through several servers. A SIP network for example comprises four types of servers: a registrar server for location registration; a proxy server for call establishment, call signal forwarding, and authentication; a redirect server for call signal forwarding; and a user-agent server.
FIG. 1 shows an example of a user (user A) with a mobile device 120 making a VoIP call to another user (user B) with a mobile device 160 via an Internet 14. In most VoIP networks, user A needs to register an account to registrar server 144 before accessing the VoIP network. User A in a Wireless Local Area Network (WLAN) 12 sends call signals through SIP proxy or redirect servers 142 and 146 via Access Points (AP) 122 and 162 to user B in WLAN 16. After several messages are exchanged through the VoIP servers 142, 144, and 146, a connection is established between user A and user B enabling. access to their network information, such as IP addresses and port numbers. User A and user B can then engage in a VoIP conversation by directly transmitting voice packets through Internet 14.
Some corporate entities establish their own SIP or H.323 networks on the Internet. These corporate entities are so called VoIP service providers. The VoIP service providers generally do not provide IP bearer services. The IP bearer services may be LAN or WLAN supported by Asymmetric Digital Subscriber Line (ADSL) or cable services providers. Customers can use LAN or WLAN, which is generally free to the public, to access s VoIP service provider VoIP network.
Maintenance of a VoIP network, however, is costly. Take a SIP network for example, the VoIP service providers must implement SIP services such as registrars, proxy servers, and redirect servers. As a result, using the conventional VoIP, consumers are forced to pay VoIP service fees to their service providers, even if the IP bearer service is free.
FIG. 2 shows typical VoIP call establishment procedures using SIP. Mobile 1 and Mobile 2 must register their accounts to a registrar by providing network information such as IP address and port number through SIP (Session Initiation Protocol) proxy 1 and SIP proxy 2 respectively. Mobile 1 must be authenticated by SIP proxy 1 before sending a SIP invite message to Mobile 2. Mobile 1 sends the SIP invite message to SIP proxy 1 with a calculated value for authentication, and SIP proxy 1 forwards the invitation to SIP proxy 2 if Mobile 1 is authenticated by SIP proxy 1. Mobile 2 replies with a SIP ringing message via the SIP proxy servers when receiving the SIP invite message. Mobile 2 sends SIP 200 OK to Mobile 1 when the user of Mobile 2 answers the call. Mobile 1 replies with a SIP acknowledgement when receiving SIP 200 OK from Mobile 2. As a result, a VoIP connection between Mobile 1 and Mobile 2 is established. The VoIP servers such as the registrar and two SIP proxy servers in FIG. 3, play an important role in establishing the VoIP connection since these servers handle call signal forwarding, user authentication, and registration.
For the above typical VoIP service, drawbacks comprise server instability, high VoIP servers maintenance cost, low compatibility, and complex procedures. Furthermore, VoIP service customers must apply for VoIP services and must pay VoIP service fees to service providers, which may be based on VoIP session duration. Customers that use different voice service providers may not be able to communicate with each other, and there may be interoperability issues as VoIP servers may be built by different vendors. Additionally, complicated registration and authentication procedures are required before a VoIP conversation can be established.